Deflector horn for high-intensity electron beams

ABSTRACT

An electron deflector horn which emits high-intensity electron beams for radiation purposes and which is connected with a deflector, an accelerator having a vacuum chamber and an electron source, includes a conical outer body portion and a conical inner body portion and an electron outlet window of annular circular configuration which separates the vacuum chamber from the ambient atmosphere. The circular electron outlet window is affixed to the conical body portions by a securing mechanism which has no parts that extend into the window area.

United States Patent 1191 Offermann l l DEFLECTOR HORN FOR HIGH-INTENSITY ELECTRON BEAMS [75] Inventor: Bernd-Peter OffermanmHamburg,

Germany [22] Filed: Aug. 24, 1973 [21] Appl. No.: 391,055

3,486,060 l2/l969 Swanson 313/74 FOREIGN PATENTS OR APPLICATIONS 39-8347 5/1964 Japan 250/398 Primary E.\'aminer-Robert Segal Almrney, Agent, or FirmSpencer & Kaye 157 ABSTRACT An electron deflector horn which emits high-intensity electron beams for radiation purposes and which is [30] Foreign Application Priority Data connected with a deflector, an accelerator having a Aug. 24. 1 72 rm ny 2241552 vacuum chamber and an electron source, includes a 1973 Gcfmlmy 7231279 conical outcr body portion and a conical inner body portion and an electron outlet window of annular cirl l 313/477 cular configuration which separates the vacuum chaml l j j j 29/86 her from the ambient atmosphere. The circular elecl l Field of Search 250/398 tron outlet window is affixed to the conical body portions by a securing mechanism which has no parts that [56] Referenc S Ci e extend into the window area.

UNITED STATES PATENTS 2,959,700 11/1960 Campanile 313 74 x 6 Clams 2 Drawmg a m TM 3 2 I I Q A 7 7 A DEFLECTOR HORN FOR HIGH-INTENSITY ELECTRON BEAMS BACKGROUND OF THE INVENTION This invention relates to an electron deflector horn designed for high-intensity electron beams used for radiation purposes and is of the type which is associated with an electron source, an electron accelerator and an electron deflection system which deflects the electrons by means of magnetic and/or electric fields towards an electron outlet window that separates the vacuum chamber of the electron accelerator from the ambient atmosphere.

Electron deflector horns have been known which have an electron outlet window of rectangular or linear shape. In order to insure that the minimum amount of energy of the exiting electrons is absorbed by the window itself, the latter should be as thin and should have an as large a surface as possible. The design of such a window is primarily dependent upon the properties, particularly the tensional strength of the material of which the window structure is made. For such purposes most often thin sheets (foils) of light metal are used. Electron outlet windows of known structure often include usually water-cooled auxiliary webs which, as window frames, serve for supporting the window foils. A window structure designed in this manner and used in an electron deflector horn is, however, disadvantageous since the webs absorb one part of the electron energy and thus adversely affect the electron-pervious properties of the window.

In designing an electron deflector horn, it has to be further taken into account that the electron outlet window and the angle of deflection of the electrons cannot be selected arbitrarily large since the electrons in the marginal window ranges pass obliquely through the window. In this manner the effective thickness of the window and thus the number of the electrons absorbed by the window increase. For this reason the length of an electron outlet window of linear configuration is limited.

SUMMARY OF THE INVENTION It is an object of the invention to provide an improved electron deflector horn of the aforeoutlined type from which the disadvantages of the known electron outlet windows are eliminated and further, electron beams of substantially higher intensity may be used than it has been possible heretofore.

This object and others to become apparent as the specification progresses is accomplished by the inven tion. according to which, briefly stated, the electron outlet window is of circular configuration and is affixed to the electron deflector horn without auxiliary webs.

It is an advantage of the invention that the electrons which pass through the electron outlet window are not absorbed by auxiliary webs but may be used entirely for radiation purposes. Compared to an electron outlet window of linear configuration having the same width and the same angle of deflection, there is obtained with a window of annular circular surface, corresponding to the ratio of perimeter to diameter. a window area which is 3.14 times larger. Consequently, the intensity of the electron beam which passes through the window is also 3.14 times greater than in prior art windows of linear configuration. A further advantage is, in addition to the compact and sturdy structure, the possibility of using relatively simple deflection means for the elec tron deflection system.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic side elevational view of a preferred embodiment of the invention.

FIG. 2 is a plan view of the same embodiment taken in the direction of arrows A-A of FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENT Turning now to the FIG. 1, there is shown an electron deflector horn which has a conical inner body portion 1 disposed in a conical outer body portion 2 in such a manner that between the two portions 1 and 2 there is defined an intermediate vacuum chamber 3, having the configuration of a conical or frustoconical shell. The components 1 and 2, as it may be observed from FIG. 2, are connected to one another by means of watercooled webs 11 which bridge the vacuum chamber 3. These webs, however, contrary to prior art structures, do not serve as a support for the electron outlet window but function merely as a mechanical connection between the inner and outer portions 1 and 2. In order to insure that only a small portion of the electrons is absorbed by the webs, it is expedient to design these webs flat and to orient them in such a manner that their narrow edge face extends transversely to the path of the electron beam. The webs 11 can be constructed like hollow bodies. In order to cool the webs II it is possible to pump water through the cavities of the webs 11. For this purpose, conventional pumps and pipe-lines can be used. It is expedient to connect two webs II with a pipe-line inside the cone of the inner body portion 1. The pipe couplings for the webs II can be arranged outside the electron deflector horn. It is, however, also possible to immobilize the two conical portions 1 and 2 with respect to one another and to obtain the intermediate spaee 3 without such webs.

The intermediate vacuum chamber 3 is, at the feet of the conical portions 1 and 2, bounded by an electron outlet window 4 which is formed of a foil separating the intermediate vacuum chamber 3 from the external ambient atmospheric pressure. The window 4 has an effective area of circular annular shape. The window 4 may be made of titanium alloys or aluminum alloys. The outlet window is affixed by means of two concentric rings 5 and 6 and by means of screws to concentric flanges 7 and 8 which, in turn, are fixedly attached to the conical portions 2 and 1, respectively. The flange 7 and the ring 5 bound the window 4 along its outer circumference, while the flange 8 and the ring 6 bound the window 4 along its inner circumference. The flanges and rings clamp the window 4 along portions externally of its effective area. It is thus seen that no mechanical supporting components extend within the outline of the effective area of the window 4, so that an unobstructed passage of the electron beam through the window 4 is ensured. The rings 5 and 6 may be made of metal, such as an aluminum alloy. In the Zone of the cone peaks of the portions 1 and 2, the intermediate vacuum chamber 3 is in communication with the inner chamber of an electron deflection system 9 which is connected after an electron generator and electron accelerator 10. The electric and magnetic electron generating, accelerating and deflecting means are not illustrated in detail.

Turning now once again to FIG. 2, there are shown the coordinate directions x and y of the deflected electrons. The electrons accelerated by the accelerator enter the deflection system 9 in which the electrons are deflected with the aid. of magnetic and/or electric fields. The deflection forces are obtained, for example, in the direction by K K cos wt and in the y direction by K,,= K sin wt. The deflected electrons pass through the intermediate vacuum chamber 3, penetrate the electron outlet window 4 and impinge upon the object to be irradiated.

Relatively simple deflection means can be used for the electron deflection system. A deflection system in which the electrons are deflected with the aid of magnetic and/or electric fields is described in German Auglegeschrift (examined patent application published for opposition) No. 1,098,630, corresponding to US. Pat. No. 2,977,500.

It will be understood that the above description of the present invention is susceptible to various modifications, changes and adaptations, and the same are intended to be comprehended within the meaning and range of equivalents of the appended claims.

I claim:

1. An electron deflector horn for high-intensity electron beams, having an electron source; an electron deflector; an electron accelerator; a horn body extending away from the electron source and defining a vacuum chamber for providing a path for the electrons emitted by the electron source and accelerated by the electron accelerator; an electron outlet window at an end of the vacuum chamber remote from the electron source, the electron outlet window separating the vacuum chamber from the ambient atmosphere; comprising in combination:

a. means defining an annular circular area of said electron outlet window, said area being exposed to the electrons travelling through said vacuum chamber;

b. an outlet portion forming part of said horn body and bounding the external circumference of said annular circular area;

c. an inner portion forming part of said horn body and bounding the internal circumference of said annular circular area; and

d. mechanical means for directly securing said electron outlet window to said horn body, said mechanical means constituting the sole support and positioning means for said electron outlet window, said mechanical means being disposed entirely externally of said area for being clear of the electron path leading to said area.

2. An electron deflector horn as defined in claim 1, said portions having a conical shape and being positioned within and spaced from, one another; said outer and inner portions together define a vacuum chamber having the configuration of a conical shell, the conical vacuum chamber having a terminal annular foot portion bounded by said electron outlet window and a terminal peak portion disposed adjacent said electron deflector.

3. An electron deflector horn as defined in claim 2, wherein said mechanical means includes flanges secured to foot portions of said inner and outer conical portions; rings, one arranged on each flange; and means clamping said electron outlet window between said rings and the associated flanges.

4. An electron deflector horn as defined in claim 3, wherein said flanges between themselves and said rings between themselves are arranged concentrically for bounding said effective area of said electron outlet window along the inner and the outer circumference thereof.

5. An electron deflector horn as defined in claim 2, including means for immobilizing the conical inner and outer portions with respect to one another.

6. An electron deflector horn as defined in claim 1, wherein said mechanical means connect said electron outlet window to said inner and outer portions of said horn body. 

1. An electron deflector horn for high-intensity electron beams, having an electron source; an electron deflector; an electron accelerator; a horn body extending away from the electron source and defining a vacuum chamber for providing a path for the electrons emitted by the electron source and accelerated by the electron accelerator; an electron outlet window at an end of the vacuum chamber remote from the electron source, the electron outlet window separating the vacuum chamber from the ambient atmosphere; comprising in combination: a. means defining an annular circular area of said electron outlet window, said area being exposed to the electrons travelling through said vacuum chamber; b. an outlet portion forming part of said horn body and bounding the external circumference of said annular circular area; c. an inner portion forming part of said horn body and bounding the internal circumference of said annular circular area; and d. mechanical means for directly securing said electron outlet window to said horn body, said mechanical means constituting the sole support and positioning means for said electron outlet window, said mechanical means being disposed entirely externally of said area for being clear of the electron path leading to said area.
 2. An electron deflector horn as defined in claim 1, said portions having a conical shape and being positioned within and spaced from, one another; said outer and inner portions together define a vacuum chamber having the configuration of a conical shell, the conical vacuum chamber having a terminal annular foot portion bounded by said electron outlet window and a terminal peak portion disposed adjacent said electron deflector.
 3. An electron deflector horn as defined in claim 2, wherein said mechanical means includes flanges secured to foot portions of said inner and outer conical portions; rings, one arranged on each flange; and means clamping said electron outlet window between said rings and the associated flanges.
 4. An electron deflector horn as defined in claim 3, wherein said flanges between themselves and said rings between themselves are arranged concentrically for bounding said effective area of said electron outlet window along the inner and the outer circumference thereof.
 5. An electron deflector horn as defined in claim 2, including means for immobilizing the conical inner and outer portions with respect to one another.
 6. An electron deflector horn as defined in claim 1, wherein said mechanical means connect said electron outlet window to said inner and outer portions of said horn body. 